Question

I am not able to concat two const char*.

I do the following:

const char* p = new char[strlen(metadata.getRoot())+strlen(metadata.getPath())];
strcat(const_cast<char*>(p),metadata.getRoot());
strcat(const_cast<char*>(p),metadata.getPath());

strcpy(const_cast<char*>(args2->fileOrFolderPath),p);

function(args2->fileOrFolderPath);

Now when I print the variable args2->fileOrFolderPath on the console then the correct output appears… But when I call a method with the variable as parameter, and work with the variable then I got a segmentation fault. What is the problem?

Answer 1

1.

const char* p=new char[strlen(metadata.getRoot())+strlen(metadata.getPath())+1];

the length plus 1 to store ‘\0’.

2.

strcpy(const_cast<char*>(args2->fileOrFolderPath),p);

You can not guarantee args2->fileOrFolderPath ‘s length is longger than strlen(p).

This works well

#include <iostream>
using namespace std;
void foo(const char*s){
    cout<<s<<endl;
}
int main(int argc,char*argv[]){
    const char* s1 = "hello ";
    const char* s2 = "world!";
    const char* p = new char [strlen(s1)+strlen(s2)+1];
    const char* s = new char [strlen(s1)+strlen(s2)+1];
    strcat(const_cast<char*>(p),s1);
    strcat(const_cast<char*>(p),s2);
    strcpy(const_cast<char*>(s),p);
    cout<<s<<endl;
    foo(s);

    return 0;
}